1. Technical Field of the Invention
The present invention relates to a method of mounting electronic components on a circuit board, whereby the mounting apparatus does not need be stopped frequently for replenishing components.
2. Description of Related Art
FIG. 2A, FIG. 3, and FIG. 4 illustrate the construction of an electronic component mounting apparatus. Parts cassettes 3 respectively accommodating electronic components of each discrete type are aligned in rows opposite each other as first and second parts feeding sections 1, 2, and electronic components fed from these first and second parts feeding sections 1, 2 are mounted onto a circuit board 5 that has been loaded into the apparatus. Mounting of electronic components onto the circuit board 5 is performed by a mounting head 6 that is mounted on an X-axis arm 7 and driven in an X direction. The X-axis arm 7 is mounted on a pair of rails 8, 8 and driven in a Y direction. The mounting head 6 is equipped with a plurality of suction nozzles 4 (three nozzles in the example shown in the drawings), and each of the suction nozzles is driven to move upwards and downwards, or to rotate around its axis on the mounting head 6. The interval of the array of spaced suction nozzles 6 is made correspondent to the distance between two adjacent parts cassettes 3 in the parts feeding sections 1, 2, so that three suction nozzles 4 can pick up three electronic components at one time. Each of the suction nozzles 4 can of course pick up an electronic component independently of the others.
The electronic component mounting apparatus constructed as described above is controlled based on a mounting program, in which the arrangement of parts cassettes and mounting order are set such that the plurality of suction nozzles 4 pick up a plurality of components at the same time in as many cases as possible. One example of such mounting procedure in the prior artxe2x80x94, wherein a plurality of suction nozzles 4 pick up several components at one timexe2x80x94will be explained by referring to the flowchart of FIG. 6. Reference numerals S51 to S60 in the drawing that will be referred to in the description below respectively represent each process step of the mounting procedure.
First, the mounting head 6 moves toward the first parts feeding section 1 (S51), and each of the suction nozzles 4 picks up electronic components respectively at the same time (S52). At the next step, it is determined whether all of the suction nozzles 4 have picked up their respective components (S53), and if yes, the procedure proceeds to the step S57, where mounting of each component onto a circuit board 5 is effectuated. The above actions are repeated unless the parts feeding section fails to feed components because of component exhaustion. When it is determined that mounting of components to one circuit board 5 has been completed (S58), the circuit board 5 is unloaded from the apparatus, while a new circuit board 5 is loaded into the apparatus (S59), and the above described actions are started again.
Meanwhile, when one or more of the components to be picked up by the plurality of suction nozzles 4 is/are exhausted, and if the second parts feeding section 2 accommodates components of the same type that has been exhausted (S54), the mounting head 6 moves to the second parts feeding section 2 (S55), so as to cause the suction nozzle 4 that has not picked up a component previously in the first parts feeding section because of component exhaustion to pick up the component of the same type that has been exhausted (S56). Thereby, all of the suction nozzles 4 hold their respective components, and the mounting procedure can be continued from the step S57 onwards.
In case the components of the type that has been exhausted in the first parts feeding section 1 are not in the second feeding section 2 either, the mounting action cannot be continued further. The apparatus is thus brought to a halt (S60) and not restarted until the components that have been exhausted are replenished.
According to the method described above, it takes time for the mounting head to move to the second parts feeding section each time one type of components of the three components that are to be picked up by the suction nozzles at one time is exhausted, and for the suction nozzles to move upward and downward twice for picking up three components instead of picking them up at one time, with attendant loss in production.
In view of the foregoing, an object of the present invention is to provide a method of mounting electronic components with which the apparatus does not need be stopped frequently because of component exhaustion so as to minimize loss in production.
According to the present invention, identical sets of parts cassettes for feeding a plurality of components to be picked up at one time by a plurality of suction nozzles are prepared in the same order in a plurality of parts feeding sections. Therefore, even when one or more of the components of a predetermined combination at one parts feeding section is exhausted, the other parts feeding section can provide the same set of components in the same order for simultaneous pick-up by the suction nozzles. While the provision of a plurality of suction nozzles offers an advantage of reducing the time for mounting operation by picking up several components at one time, such advantage cannot be taken when one of the components is exhausted, whereupon simultaneous pick-up of several components is no longer possible. The present invention method enables mounting operation to be continued even when components are exhausted at one parts feeding section, with attendant enhancement in production.